From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A08C6154454 for ; Thu, 17 Oct 2024 08:51:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729155091; cv=none; b=KPHHZijjC0E2kl2zMJWhL+3KePlaChYouxMtUK9JmGzhSoeYXSz4Sb0QgbAeyQSUu0L5JOH1xM6qeIjMWQrCjjLIGkQLKgstduAoWjKcCzfBcN2o9yjmNlHLCZ12Op8agj93aEE1abwvFdE1XGqkhf+Z+h/lhMwEQqiSY4P0x3M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729155091; c=relaxed/simple; bh=hSRcn9gRi+91P5hs8fRDo4gEPJR7TvticdGrlQUqw5g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UO7zWc2ITvJNbA0aG0OL8Av197/fDHiq1No0+qyGiLjGBvKOX1DfLu6ufLwKqaJ+3RUKthhqWSk2Tt003dAFx5r3AswKvZ1l6fiJmmTpfXmkeS3OW7lUM74zwavGWpEMyoAPNLwu6UC6iW8Ikgboyhoix2tfUgvqTwSZiG1s8CE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=c8wePuxR; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="c8wePuxR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1729155086; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=EN/Eizswj47pmoV3qDsAgb+fvVuBqxHIhwGCCsZ/BBk=; b=c8wePuxRR8/9O9iFsYRE5HqQ83CXitGvKKBwrcAlWAR/OchSizFadNZwSWgOYsSEoJAFoU aR2/6PZymr3dZDeJYkOF/8eiaayYolODJ6lG2IG1kRKDkvcmB9SUakKL+czY1mtLkYpC6C ZJrCbWPIC9tZCDOEH5UhH3P8gwVNH+0= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-451-mSYxazipNm-KDe6eOCmAzQ-1; Thu, 17 Oct 2024 04:51:24 -0400 X-MC-Unique: mSYxazipNm-KDe6eOCmAzQ-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-43056c979c9so5642485e9.1 for ; Thu, 17 Oct 2024 01:51:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1729155084; x=1729759884; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=EN/Eizswj47pmoV3qDsAgb+fvVuBqxHIhwGCCsZ/BBk=; b=XED5RuDQPyYgMG0SuPrae2O+0rKKv72HfAxJwf5e5x1Pdk6dFNjPXPqnlKe2oiD9nB nww0ssxtwizOALepiTGv/ZjZouctpdCRm8pozYutMDIQ+kym3Kf4qSNt27VFl+fmtvoK Y5VOQm7+5SSgFvgk+z5BKFuiykjrr0JPBB3ggSIbE6O8pKluzIL/p7dGF4HinS7yIAwc ytjeJLKvq5Cl/8OWBPP4QkKvflnpAV3b9Dc/fLuyfy7NhA0nlfDhoVCErW6L28LTVQuw Ryc6y5v20EyUvtqHAyIYir1leevm1GCucpDY3k0ak5eLk1CCRFsNBgtVmB9WMkuvRaRj psWg== X-Gm-Message-State: AOJu0YyWzlYxqn9XRojCkBvXIwGOFRosPGwaOfihexPsnS5OR8CK0pVS xPVBFoaHOxS9V9U2bAkQj9V4jNyNQKv//YUxy/isRr7b7FwZRnb/Lm6a9gXkgLnF9A2g5LED9hp Vbd8YPbP0gsaapJdC2JnZ1FzwFEL43E+3OS3Aec6LzCF0UNl2EnCzbKVg3+9j1A== X-Received: by 2002:a05:600c:3c9c:b0:42c:e0da:f15c with SMTP id 5b1f17b1804b1-4314a32333bmr50976105e9.20.1729155083677; Thu, 17 Oct 2024 01:51:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGYYhBoPFvFWP0XlaQg+uyhe3vARcgCr9/+6i0JB3VhiAXicmKPY9C+kRks11rZ04Pl5CnMrA== X-Received: by 2002:a05:600c:3c9c:b0:42c:e0da:f15c with SMTP id 5b1f17b1804b1-4314a32333bmr50975865e9.20.1729155083293; Thu, 17 Oct 2024 01:51:23 -0700 (PDT) Received: from ?IPV6:2003:cb:c705:7600:62cc:24c1:9dbe:a2f5? (p200300cbc705760062cc24c19dbea2f5.dip0.t-ipconnect.de. [2003:cb:c705:7600:62cc:24c1:9dbe:a2f5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37d7fc12dbcsm6666212f8f.96.2024.10.17.01.51.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Oct 2024 01:51:22 -0700 (PDT) Message-ID: <1f8dcae1-416e-43cf-8dda-5440e0db4c00@redhat.com> Date: Thu, 17 Oct 2024 10:51:21 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/gup: stop leaking pinned pages in low memory conditions To: John Hubbard , Andrew Morton Cc: LKML , linux-mm@kvack.org, Alistair Popple , Shigeru Yoshida , Jason Gunthorpe , Minchan Kim , Pasha Tatashin References: <20241016202242.456953-1-jhubbard@nvidia.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20241016202242.456953-1-jhubbard@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 16.10.24 22:22, John Hubbard wrote: > If a driver tries to call any of the pin_user_pages*(FOLL_LONGTERM) > family of functions, and requests "too many" pages, then the call will > erroneously leave pages pinned. This is visible in user space as an > actual memory leak. > > Repro is trivial: just make enough pin_user_pages(FOLL_LONGTERM) calls > to exhaust memory. > > The root cause of the problem is this sequence, within > __gup_longterm_locked(): > > __get_user_pages_locked() > rc = check_and_migrate_movable_pages() > > ...which gets retried in a loop. The loop error handling is incomplete, > clearly due to a somewhat unusual and complicated tri-state error API. > But anyway, if -ENOMEM, or in fact, any unexpected error is returned > from check_and_migrate_movable_pages(), then __gup_longterm_locked() > happily returns the error, while leaving the pages pinned. > > In the failed case, which is an app that requests (via a device driver) > 30720000000 bytes to be pinned, and then exits, I see this: > > $ grep foll /proc/vmstat > nr_foll_pin_acquired 7502048 > nr_foll_pin_released 2048 > > And after applying this patch, it returns to balanced pins: > > $ grep foll /proc/vmstat > nr_foll_pin_acquired 7502048 > nr_foll_pin_released 7502048 > > Fix this by unpinning the pages that __get_user_pages_locked() has > pinned, in such error cases. > > Fixes: 24a95998e9ba ("mm/gup.c: simplify and fix check_and_migrate_movable_pages() return codes") > Cc: Alistair Popple > Cc: Shigeru Yoshida > Cc: David Hildenbrand > Cc: Jason Gunthorpe > Cc: Minchan Kim > Cc: Pasha Tatashin > Signed-off-by: John Hubbard > --- > mm/gup.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index a82890b46a36..24acf53c8294 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2492,6 +2492,17 @@ static long __gup_longterm_locked(struct mm_struct *mm, > > /* FOLL_LONGTERM implies FOLL_PIN */ > rc = check_and_migrate_movable_pages(nr_pinned_pages, pages); > + > + /* > + * The __get_user_pages_locked() call happens before we know > + * that whether it's possible to successfully complete the whole > + * operation. To compensate for this, if we get an unexpected > + * error (such as -ENOMEM) then we must unpin everything, before > + * erroring out. > + */ > + if (rc != -EAGAIN && rc != 0) > + unpin_user_pages(pages, nr_pinned_pages); > + > } while (rc == -EAGAIN); Wouldn't it be cleaner to simply have here after the loop (possibly even after the memalloc_pin_restore()) if (rc) unpin_user_pages(pages, nr_pinned_pages); But maybe I am missing something. > memalloc_pin_restore(flags); > return rc ? rc : nr_pinned_pages; -- Cheers, David / dhildenb